1. Field of the Invention
This invention relates to a rotor of an electrical machine, especially a turbine generator, where the rotor winding is placed into grooves and secured against forces developing during operation by means of shrunk-on rings of nonmagnetic metal.
2. Description of the Prior Art
The limiting output of, for example, two-pole turbine generators has been increased during the past 30 years from about 100 to 1000 MVA, whereby the dimensions of the machines did not have to be even approximately enlarged to the same degree. This development was mainly made possible by means of better and better cooling methods and, caused by this fact, a better utilization of the active conductor material (water cooling) and, to a lower degree, by means of using better materials and production methods.
An additional step in the direction of an increase in the generator output is shown in the magazine "Elektrotechnik und Maschinenbau" (Electrical and Constructional Engineering) 89 (1972), Issue 1, pages 1-11, or in the AT Patent 292,833, respectively. Since the synchronous reactance becomes larger and larger with an increasing utilization of the machine, it is there proposed to design stator and rotor without teeth instead of making the air gap larger and larger. With such a design, the ironless winding space replaces the air gap to a large extent. In the toothless rotor, the winding conductors are arranged on top of each other in their straight portion in several layers limited by cylinder jacket surfaces. The conductors of radially adjacent layers are each staggered in this instance in the circumferential direction by one half of the conductor width. The rotor has a plurality of crossbars which serve the purpose of transmitting the momentum and of producing a concentric seat for a jacket of nonmagnetic steel which consists of overlapping tubes and which is shrunk on the rotor. This steel jacket, besides fastening the winding, has the task to relieve the shaft.
A rotor without teeth is also known from the German Publication 25 00 782, where the rotor winding is fixed by means of rings and expansible devices (rings filled with synthetic resin under pressure and hardened) arranged between the rings and the winding.
The proposals describing a turbine generator completely without teeth in "Proc. IEE", Vol. 120, No. 12, December 1973, pages 1507-1518, aim in the same direction. The rotor winding is arranged on an entirely smooth steel cylinder and is held in place by means of bindings or rings or steel, titanium or carbon fiber-reinforced plastics.